A thin film transistor liquid crystal display (LCD) device has many advantages of thin body, power saving, no radiation, so it obtains wide range application. Most of the liquid crystal devices in current market are backlight type liquid crystal display, which includes a liquid crystal display panel and a backlight module. The working principle of the liquid crystal display panel is: placing liquid crystal molecules in two parallel glass substrates, which have many vertical and horizontal fine wires between the two glass substrates; controlling the liquid crystal molecules to change direction by energizing or not energizing; and refracting light of the backlight module to produce frames.
Generally, the liquid crystal display panel is consisting of a color filter (CF) substrate, a thin film transistor (TFT) substrate, liquid crystal (LC) interposed between the CF substrate and the TFT substrate, and a sealant. In TFT-LCD, classifications based on operation modes of the liquid crystal have phase change (PC), twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), and in plane switching (IPS), etc. For the purpose of the common VA display mode, it is needed that a transparent conductive film is simultaneously and respectively disposed on a side, facing the liquid crystal layer, of the CF substrate and the TFT substrate, a main function of the transparent conductive film is to form an electric field between the CF substrate and the TFT substrate, and to drive deflection of the liquid crystal molecules, so as to achieve bright and dark display.
Currently, the conventional transparent conductive film is indium tin oxide (ITO) film prepared by methods of physical vapor deposition (PVD). Additionally, after the transparent conductive films on the TFT substrate and the CF substrate are formed, an alignment film of tens to hundreds nanometers thickness is usually coated or printed thereon, when liquid crystal (LC) is contacted with the alignment film, LC can be allowed to form a pre-inclination angle at a certain direction, so as to provide a load angle for the liquid crystal molecules (a size of the pre-inclination angle has an important influence on driving voltage, contrast ratio, response time, viewing angle of TFT-LCD).
A material of the alignment film is usually chosen polyimide (PI) material, which is mainly classified as rubbing alignment type PI material and an optical alignment type PI material; however, no matter what the type of alignment material is, it has its own shortcoming.
Graphene has excellent transparent conductive and mechanical performances, there are many patents disclose that the graphene is used as transparent conductive films. Methods of forming the transparent conductive graphene layer can be chemical vapor deposition (CVD), CVD-transfer, graphene solution printing, and graphene oxide solution printing-reduction. However, in such patents, the graphene is only used as the transparent electrode layer; after that, it is still needed to perform material and process of the alignment film.